1. Field of the Invention
This invention relates generally to semiautomatic gun mainspring recoil systems, and more specifically to a recoil spring system with improved lock-up, rebound, and reduced muzzle rise with minimal impact.
2. Description of the Related Art
FIG. 2 is shows a typical semiautomatic gun recoil spring that traditionally uses a guide rod 204 and mainspring 202 with enough force suitable to offset the force of the blowback of the slide, and allow proper cycling of action. If the spring 204 is too light, the slide velocity can reach high enough values to result in an impact on the frame that can cause premature wear, damage or failure to the firearm, and injury to the firearm operator. If the spring 204 is too heavy, the gun may not cycle properly and be prone to misfeeds or gun jamming. Typically, semiautomatic handguns use between ten (10) to twenty (20) pound springs. While up to 28-pound springs have been used to address the heavier recoil associated with higher power factor loads, they are seldom used, as they are extremely difficult to operate. The high spring pressure makes it too difficult to manually operate the slide and/or slide-stop/release. Additionally, these heavy springs do not facilitate proper functioning of light loads, and many firearm operators either lack the physical strength, or prefer not to exert the physical energy required to operate a firearm utilizing a higher than a 17-pound mainspring. These heavy springs create a number of challenges, especially when shooting light or low power loads, and heavy or higher power loads in a gun. Reliable feeding of 9 mm semiautomatic handguns is particularly difficult if the desire is to ensure a range of standard 9 mm light target loads through 9 mm +P heavy loads. These loads typically represent around 300 foot-pounds (ft-lbs) of energy for SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) standard loads, and 400 ft-lbs of energy for 9 mm +P loads. Efforts to produce lighter, smaller, and more powerful semiautomatic handguns have been limited by the physics of recoil. To deal with more recoil, more weight or stronger spring force is required. The use of heavier springs becomes unmanageable at some point, as it increases the difficulty in releasing the slide stop/release from a locked back position to open the slide.
Advances in metallurgy, powders (propellants), and improved acceleration methods have introduced additional problems. For example, cartridges can now produce more ft-lbs of energy than what the frame of a gun may be able to withstand. This is especially true for designs that attempt to concentrate more energy into smaller, more compact, concealable semiautomatic handguns. The problem is even more pronounced with the rise in popularity of lighter, less expensive polymer frames, which are not as strong as their metal counterparts, and lack the weight to absorb the energy-transfer from the recoil. More and more higher-pressure variants of modern cartridges are being introduced. The 45 ACP (Automatic Colt Pistol) for example, has evolved from 45 ACP (21,000 PSI), 45ACP+P (23,000 PSI), 45 Super (28,000 PSI), 0.460 Rowland (40,000 PSI), and 45 Coffman (50,000 PSI). While the pressure may have doubled, the ft-lbs may have tripled, as in the case of standard 9 mm, typically 300 ft-lbs, and the 9 mm Coffman at 967 ft-lbs. The operation of firearms with lower recoil, the use of less expensive ammunition in a “Magnum” variant of a semiautomatic firearm, as well as the rise in popularity of suppressors that reduce the blowback force necessary to operate the firearm necessitate the installation of lighter springs, which leads to the need for an improved method capable of addressing such a wide range of slide velocities while providing proper lock-up.
Current improvements have centered on incorporating a full-length spring inside another spring, or employing a dual-spring system. An example is provided in FIG. 3, where a spring assembly 300 includes a full-length spring 304 incorporated inside another spring 302 to help progressively dampen the recoil throughout the full length of the guide rod/enclosure 306. Another example of a dual spring assembly 402 is shown in FIG. 4. More specifically, FIG. 4 illustrates a captured dual spring assembly that includes a captured light and heavy progressive stack Glock Gen4. Even in progressive spring systems the spring force increases substantially prior to the last (approximately) ¼″ of travel, thus increasing the force required to depress and release the slide stop, which is the primary reason that over 20-pound springs are seldom used. This is illustrated in FIG. 12, which shows a semiautomatic handgun to illustrate the over-travel with respect to the slide-stop. As indicated in FIG. 12, in a closed state 1200 of the handgun, the breech is closed (indicated by 1210 and 1212), whereas in an open state 1202 of the handgun the slide is locked in place by the slide stop (indicated by 1214). In an over-travel state 1204, the travel is beyond the slide stop, which is further illustrated in magnified area 1220, which shows the slide stop lever on the frame at the left arrow of 1222, with the slide stop notch in slide shown at the right arrow of 1222. The slide stop lever 1224 has a tab that is pushed upward by the magazine follower when the last round is fired, basically catching or stopping the slide from advancing forward, hence the name slide stop, which indicates to the firearm operator that the firearm is empty. In the locked back position, once the operator has inserted a new magazine, the slide stop lever may be depressed, releasing the slide to move forward. This too is very difficult to perform one handed (which is nonetheless the preferred method of operation) if the main spring force is above 17 pounds.
In the case above, all of the recoil above the 20+ pounds of force is directed into the frame of the firearm and into the operator's body. This excessive impact causes the slide to dwell in the recoiling motion until both the frame and operator absorb the recoil until such a time as the main spring(s) recover and redirect the slide forward. FIG. 5 provides an example of another method that involves the use of buffers 502 to absorb the excess force of impact. Buffer 502 may be situated within a spring assembly as shown within a handgun 552. FIG. 6 provides an illustration of another type of buffer 604 that may be used on a guide rod 602 in a guide rod assembly 610. The guide rod 602 may be used with mainspring 606 and buffer 604 in a gun 608 as also shown in FIG. 6. FIG. 7 shows yet another example of a buffer 706 placed on a guide rod 708 in the rod assembly 702, and shown with a spring in assembly 752. While the buffer method is somewhat effective in buffering the forces that might damage the frame from metal-on-metal contact, they barely, if at all, absorb or decelerate the main force of impact, again relying on the frame and the operator to absorb these forces and allow the mainspring to recover. Such buffers are typically made of urethane or elastomer materials, which are prone to premature wear usually limited to 100-1200 rounds of ammunition. In tests conducted with a high-pressure variant of the 0.380 ACP (200 ft-lbs), and the 380 Coffman (420 ft-lbs) in a Sig Sauer P238, the buffer lasted less than ten shots due to lacerations from the slide stop. Additionally, while elastomer buffers do provide some energy absorption, the rebound force is virtually non-existent.
Most semi automatic firearms will facilitate the use of lighter springs to ease the manual operation by user and increase slide velocity for improved cycling. While some multi-spring combinations reduce the spring weight needed, the gun design and size may necessitate a higher spring weight than is comfortable or physically possible for some people to operate. This is especially true of the industries movement to the internal striker design and more compact polymer frame pistols. The micro compact polymer frame firearms lack the weight to adequately deal with the recoil necessitating an even heavier spring. The internal striker design consistent with Glock pistols necessitates heavier springs, since in such a design the striker/firing pin spring and the main spring inherently oppose one another. While a conventional semiautomatic firearm may only need a 11-pound to 15-pound spring to remain securely in battery instance, the internal striker design would dictate an 17-18-pound mainspring, so when the 5.5-pound firing pin spring is under load and opposing the 18-pound mainspring, a net effect of 13.5 pounds of force remains to keep the gun securely in battery.
There exists therefore a need for improved ease of operation of firearms while maintaining proper lock-up, increased slide velocity and rebound energy with reduced impact and muzzle rise in semiautomatic weapon recoil systems.